Transformer core assembly

ABSTRACT

A transformer core assembly including a plurality of laminations of magnetic material which are releasably clamped together into a unitary structure. The core includes a number of leg sections which are joined together by a number of yoke sections. The leg and yoke sections are formed of stacked laminations of magnetic material Support bars are positioned against one edge of one yoke section and are slidable received in a pair of clamp members. The clamp members are positioned against opposite sides of the yoke section and are bolted together tp confine the yoke section therebetween. Another pair of clamp members bear against the sides of the other yoke section and are bolted together to clamp that yoke section therebetween. A J-bolt interconnects one corner of each of the first clamp members with a corresponding corner of each of the other pair of clamp members and each of the other clamp members is provided with an opening to receive lifting mechanism adjacent the J-bolt.

[ Sept. 18,1973

United States Patent [1 1 Czewski et al.

[ TRANSFORMER CORE AS SEMBLY Primary Examiner-Thomas J. Kozma [75 Inventors: Robert L. Czewski' Robert Gross Attorney-Radford M. Reams et al.

Ind.

ABSTRACT A transformer core assembly including a l both of Fort Wayrle Fort plurality of aminations of magnetic material which are releasably [73] Assignee: General Electric Company,

' Wayne, Ind.

clamped together into a unitary structure. The core in- [22] Filed: Feb. 5, 1973 cludes a number of leg sections which are joined together by a number of yoke sections. The leg and yoke [21] Appl. No.: 329,886

sections are formed of stacked laminations of magnetic material Support bars are positioned against one edge of one yoke section and are slidable received in a pair of clamp members. The clamp members are positioned against opposite sides of the yoke section and are mH L WC t Uh ll 21 55 ll [58] Field of Search....... 336/210; 310/217 bolted together tp confine the yoke section therebe- [56] References Cited UNITED STATES PATENTS tween. Another pair of clamp members bear against the sides of the other yoke section and are bolted together Aldridge, 336/210 to clamp that yoke section therebetween. A J-bolt in- 969 Derbyshire et al. 336/210 X terconnects one corner of each of the first clamp mem- 933 Brand 3 X b'ers with a corresponding corner of each of theother Wagner-m 336/210 pair of clamp members and each of the other clamp figgzj 'j' members is provided with an opening to receive lifting mechanism adjacent the Lbolt' 6 Claims, 5 Drawing Figures TRANSFORMER CORE ASSEMBLY BACKGROUND OF THE INVENTION In large stationary induction apparatus, such as large dry-type transformers for example, the core ordinarily is formed by stacking a number of laminations of magnetic material such as grain oriented steel. Typically such cores have one or more legs or leg sections about which coils of conductor are mounted, with each end of the legs being connected by yoke sections. Byway of example, a typical three phase transformer has three winding legs, the ends of which are interconnected by elongated yokes or yoke sections. In forming a typical three phase transformer E and I laminations are used and the location of the E and the I laminations are alternated from layer to layer to provide an interleaved structure, as is well known in the art. It is desirable that the individual laminations be held in a tightly compacted mass to provide optimum paths for the magnetic flux. A number of magnetic materials, particularly grain oriented steel for example, are: very sensitive to bending or flexing. If the laminations are bent or flexed as a result of uneven pressure applied during the assembly or handling of the core, the characteristics of the material will be changed and will increase the core losses during operation of the apparatus. For a number of years, particularly in smaller size devices, core bolts were used. to hold the cores together. This necessarily provided a concentration of pressure at the bolt holes. Such pressure tended to flex thelaminations somewhat with an attendant adverse effect on core loss.

Magnetizing losses in such bolted cores were increased: further by the stresses generated when the coresare lifted. Large laminated structures of this type were usually picked up by a mechanized lifting apparatussuch asa crane. Thelifting apparatus was attached been welded, boltedor both weldedand bolted. Such frames have not been completely satisfactory.

Coresfor any particular transformer design aremanufactured with a specified weight of laminations-and stack height. The thickness of 'the lamination forming material varies and lamination stacking processes are not exact. Thus, after a transformer has been completely, assembled,it often'is necessary to make adjustments-in the core. In order. todo this it is necessary to relieve the. clamping forcesfrom the core.

Withia weldedor'partially welded frame'any core adjustmcnt requires that the welds be broken. Almost invariably this requires that the first clamps be scrapped and-replaced with new'clamps. Additionally, at least most weldedframes require preassembly of portions of the frame. This results in multiple assembly stations, which complicates the manufacturing process. In-any event, such approaches require a skilled welder and expensive welding equipment;

Many priorart frames ofthebolted-type include bolts which pass-through the lamination stack and thustend to cause localized areas of excess pressure. Many bolted frame, approaches are such that core. adjust-- mentsare possible only by completely disassembling drawing the first pair of clamp members together to the frame. Bolted frames tend to exert uneven or excessive clamping pressure to prevent the core from slipping out of position. This can cause distortion of the laminations. Many bolted frames include a number of spacers between the core and clamping members to assure uniform clamping action. Such spacers are usually located on the top and bottom of the top and bottom yoke sections respectively. Such spacers hinder minor core adjustments and complicate handling.

Any of the prior art frames, whether welded or bolted, that involve pre-assembly require special fixtures to store and/or transport the core and coil assembly without the unit tending to fall over or come apart.

SUMMARY OF THE INVENTION It is, therefore, an object of thepresent invention to provide a new and improved core assembly which is releasably secured into a unitary structure.

It is another object" of the present invention to pro-' vide such a core assembly which may easily be disassembled and reassembled.

It is still another object of the present invention to provide such a unitary core assembly with which an applied lifting force acts upon the lower portion of the core.

It is yet another object of the present invention to provide such an improved coreassembly in which the same size individual components may be utilized with a number of different cores.

It is yet another object to provide an improved core assembly in which: adjustments to the core may be made without complete disassembly of the clamping frame.

It isstill another object'to provide an improved core assembly which may be moved and stored without' special fixtures. y

The present invention, in accordance with one embodiment thereof, provides a transformer core assem bly comprising plurality of leg sections and thepluralit'y of yoke sections joining the end of theleg sections. The leg sections and the yoke sections are formed of stacked laminations of magnetic material; A first pair 'ofelongated clamp members extend along opposite sidesof a first yoke section. Locking means extend between the first pair ofelongated clamp members, beyond each end of the first yoke section, for releasably clamp the first yoke section therebetween. A plurality of elongated support bars are slidably received in each of the first pair of clamp-members and extend therebetween'inengagement with thefirst yoke section.

The above-mentioned and other features'andobjects of this invention, as well as the manner of obtaining them, will become more apparent, in the invention it'- self and will be more fully understood by reference to the followingdescription taken in conjunction with the accompanying drawing, wherein:

BRIEF DESCRIPTION OF THE DRAWING- FIG. I is a somewhat schematic perspective view from the front of'a core and coil assembly for'a*drytype transformer embodying one form of our invention;

FIG. 2 is an end view of the core clamping'and' lifting of FIG. 1, with the core and coil removed for purposes of illustration;

FIG. 4 is an exploded perspective view of a core using E and I laminations and illustrating a preferred placement of the support bars; and

FIG. 5 is an exploded perspective view ofa core using various length I laminationsand illustrating a preferred placement of the support bars.

DESCRIPTION OF THE PREFERRE EMBODIMENTS 1 Referring now to the drawing, and particularly to FIG. 1, there is shown a three phase transformer embodying one form of the present invention. The illustrative transformer 10 is dry-type transformer adapted for operation without immersion in insulating oil or the like. It includes a core 11 formed of a stack of laminations of magnetic material such as grain oriented steel, for instance. The core 1 1 includes three coil or winding receiving legs 12, 13 and 14 which are generally verticallydisposed in FIG. 1. Each end of the coil receiving legs are interconnected by yokes or yoke sections 15 and 16 respectively.

Each of the legs 12-14 has a set of electrical coils or windings 17, 18 and 19 respectively, fitted thereon. Typically each set of coils 17-19 includes at least one high voltage coil and a related low voltage coil. The coil sets normally are performed and then the laminations forming a core are interleaved with the laminations forming the legs passing through the center openings of the coils to form the transformer. With such a construction the core 11 supports the coils 17-19 and provides paths for flux generated when the coils are energized.

The core is mounted in a clamping and lifting frame assembly which is designed to firmly support the core.

ture which may be easily disassembled as for alterations in the core during manufacture. Moreover, minor alterations of the core may be made without disassembly. Often a transformer which does not perform within the design specification can be made to do so by pounding." That is by hitting the edge of one yoke with a rubber or other soft hammer. With the present arrangement the upper edge of yoke 15 is exposed and the core effectively can be pounded merely by slightly loosening the clamp members 34, 35.

The sides of the lower yoke section 16 are positioned between a first pair of clamp'members 20 and 21. Each of the clamp members is L shaped in cross section. Clamp 20 has a first side or portion 22 which fits in juxtaposition to andextends along one side of yoke 16 and a second side or portion 23 which extends generally perpendicular to the outer side of yoke 16. Similarly clamp-21 has a first side or portion 24 which fits in juxtaposition to and extends along the, outer side of yoke 16 and a second side or portion 25 which extends generally perpendicular to the yoke 16.

Each of the clamp members 20 and 21 is apertured as seen at 26 and 27 respectively. There are a plurality of elongated support bars 28 which preferably are generally rectangular-in cross section so as to present a flat surface for engagement with the end of yoke 16. Each of the support bars 28 is slidably received through one of the apertures 26 and clamp member 20 and a corresponding aperature 27 in clamp member 21. There also is provided locking means in the form of threaded bolts 29 and cooperating nuts 30. The bolts 29 extend be- The core and frame form an essentially unitary struc- I tween the two clamp members 20 and 21 with the head of the bolt to the outside of one of the clamp members and with the nut positioned to the outside of the other clamp member.

The portion of the clamping and lifting assembly thus far described is positioned around the yoke section 16 with the bottom edge (as seen in FIG. 1) of the yoke engaging on the support bars 28 and with the clamp members 20 and 21 positioned outside the yoke. The bolts 29 and nuts 30 are then tightened to bring the first sides or portions 22 and 24 into firm engagement with the sides of the yoke 16. This firmly holds or clamps yoke 16 between the clamp members 20 and 21 in engagement with the support bars 28. It will be seen from FIG. 1 that the bolts 29 pass between the clamp members 20 and 21 beyond the ends of the yoke 16 so that no bolt holes need be provided in the laminations.

A second set of similar clamp members 31 and 32 are provided for clamping the other or top yoke 15. The clamp members 31 and 32 also are generally L shaped in cross section. Clamp member 31 has a first side or portion 33 which extends in juxtaposition to one side or yoke 15 and a second side or portion 34'which extends generally perpendicular to yoke 15. Similarly, clamp member 32 has a first side or portion 35 which extends in juxtaposition to the other side of yoke 15 and a second side or portion 36 which extends generally perpendicular tothe yoke 15. Locking means in the form of bolts 37 and nuts 38 are provided for the second set of clamp members and draw the clamp members 31 and 32 together with yoke 15 firmly clamped between clamp member sides 33 and 35. The bolts 37 extend between the clamp members 34-35 beyond the ends of the yoke 15 so that yoke 15 does not have to be provided with bolt holes.

It will be noted that at least one end of clamp member 20 and the corresponding end of clamp member 31 extend well beyond the associated lokcing bolts and that the ends of clamp member 21 and clamp member 32 at diagonally opposite corners of the associated yoke extend well beyond their associated locking bolts. These extended ends of each of the clamp members are utilized forconnection of force transfer means including J-bolts 39 and 40. It will be noted that side 22 of clamping member 20 is provided with a generally vertically elongated aperature 41 and side 34 of clamp member 31 is provided with an opening 42. Once the two sets of clamp members have been drawn together so as to firmly engage the yokes therebetween the hooked end 43 of J-bolt 39 is inserted through the opening 41 in clamp member 20 and the threaded end 44 is inserted through the opening 42 in clamp member 31 far enough to cause hooked end 43 to engage the top of aperature 41. Thereafter, 45 and 46, which are mounted on the J-bolt 39, are tightened against the side 34 of clamp member 31. This firmly interconnects the corresponding ends of clamp members 20 and 31.

The extended ends of clamps 21 and 32 are provided with corresponding openings 47 and 48 respectively. The hooked end 49 of J-bolt 40 is insertedthrough the opening 47 and the threaded end 50 of the J-bolt is inserted through the opening 48 far enough to cause hooked end 49 to engage the top of apperature 47. Thereafter, nuts 51 and 52, which are mounted on the threaded end 50 are tightened against portion 36 of clamp member 32. This firmly interconnects the corresponding ends of clamp members 21 and 32.

With such an arrangement the upper of clamp members are firmly connected to the lower clamp members and the support bars so that a lifting force applied to the upper clamping members will be transferred through the 1- bolts to the lower clamping members and support bars and the transformer will be lifted through the support bars 28. This minimizes any bending or other unusual stress being placed upon the transformer during a lifting operation. This lifting may be best accomplished by applying the lifting force to the upper clamp members 31 and 32 in the areas adjacent their interconnection with the corresponding J-bolt. To this end the clamp side 33 is provided with an opening 53 and the clamp side 35 is provided with an opening 54 by which a suitable lifting mechanism may be attached for lifting the transformer. A portion of such a suitable mechanism is illustrated in FIG. 1 by the lifting hooks 55 and chain 56.

The support bars are sized and positioned to provide support for all of the laminations in the core. FIGS. 4 and 5 illustrate suitable arrangements for two typical core constructions. Turning first to FIG. 4 there is shown a typical EI core; that is, a core formed from a combination of E shaped and I shaped laminations. Each E lamination 60 includes a long leg 61' and a pair of short legs 62, all joined by a base or yoke 63. The I laminations 64 are sized to overlie the distal ends of the short legs 62 and abut against the distal end of long leg 61'. The laminations are alternated from layer to layer so that the long legs 61 are on opposite sides in adjacent layers. With such an arrangement two support bars 28 will support all the laminations. To this end each support bar is spaced slightly inwardly from one side of the core so as to underlie the abuttment between the long leg 61 and I lamination in corresponding alternate layers. It also supports the other end of the lamination in adjacentlaminations.

FIG. 5 shows a similar core formed from a number of I laminations 65, 66, 67 which have cooperating lengths. The arrangement of the individual laminations is alternated between top andbottomin adjacent layers. With this arrangement three support bars 28 provide support for all of the laminationslt will be obvious that other lamination shapes and arrangements may require other support bar arrangements.

It will be understood that in accordance with the present invention, as illustrated by the exemplification embodiment, a number of advantages are obtained. For instance, the elongated clamping members 20, 21, 31' and 32 include flat sides or portions which are in juxtaposition to the sides of the yokes and present relatively broad flat surfaces that-bear against the yoke. This arrangement exerts clamping forces on the core which are spread over large areas and do not create localized stresses. Also, when the transformer is moved the lifting force is applied to a very large degree by the support bars 28. These bars have the dual advantage of being on the bottom of the core and presenting large flat surfaces to the edge of the yoke. It will be understood that a number of different transformers may be manufactured using these same components for the clamping lifting mechanism. For instance'where a number of related cores differ'only in the stack height, that is the side to side dimension of the core, all of the commade long enough to adequately overlap clamp sides 23 and 25 with a transformer of the largest stack height. With transformers of smaller stack height there is merely greater overlapping of the support bars 28 and clamp'members. Also a number of cores with different core lengths, from the outside of one end winding leg to the outside. of the other end winding leg, may utilize the same components with the clamp members merely being designed to be sufficiently long and with the openings for the locking bolts sufficiently far apart to accept the longest core. Of substantial importance is the fact, that while the clamping and lifting frame as sembly firmly engages the core so as to form a unitary core assembly, the clamping and lifting frame assembly is easily disassembled after the transformer has been completed. Thus, if a transformer is completely assembled and a subsequent test indicates that certain of the laminations may not be inadequate engagement, or that additional laminations should be provided or that some laminations should be removed, the clamping and lifting frame assembly is easily removed and then reconnected after appropriate action on the core.

.While in accordance with the patent statute, there has been described what at present is considered to be the preferred embodiments of this invention, it'- will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. It is applicants intention in -the following claims to cover all such equivalent variations which fall within the true spirit and scope of the invention. I What'we claim as new and desire to be secured by Letters Patent of the United States is:

.l.A transformer core assembly comprising: A plurality of leg sections and aplurality of yoke sections joining the ends of said leg sections; said leg sections and said yoke sections being formed of stacked laminations of magnetic material; a first pair of elongated clamp members extending parallel to opposite sides of a first yoke section; locking means extending between said first pair of elongated clamp members beyond each end of said first yoke section for releasably drawing said first pair "of clamp members together to clamp said first yoke section therebet'ween; a plurality'of elongated sup"- port bars slidably received in each of said pair of clamp members and extending thereb etween in en: gagement with the outer periphery of said first yoke section, said support bars beingsized and positioned to support said laminations forming said leg and yoke sections.

2. A transformer core assembly asset forth in' claim 7 3. A transformer core assembly as set forth in claim 2, further comprising: force. transfer means positioned adjacent at least'two, diagonally opposite corners of said transformer assembly and interconnecting predetermined ones of one of said pairs of clamp members with corresponding ones of the other of said pair" of clamp members.

4. A transformer core assembly as set forthin claim 3, wherein: each of saidclamp members includes a first portion extending in juxtaposition to the corresponding yoke section and a second portion extending normally to the corresponding yoke section; said force transfer means includes a plurality of elongated bolts; each of said bolts being interconnected with a first portion of one of said first pair of clamp members and interconnected with a second portion of a corresponding one of said second pair of clamp members.

5. A transformer core assembly as set forth in claim 4, wherein: each of said second pair of clamp members defines means for connection of a transformer core lift mechanism adjacent the interconnection that one of section. 

1. A transformer core assembly comprising: A plurality of leg sections and a plurality of yoke sections joining the ends of said leg sections; said leg sections and said yoke sections being formed of stacked laminations of magnetic material; a first pair of elongated clamp members extending parallel to opposite sides of a first yoke section; locking means extending between said first pair of elongated clamp members beyond each end of said first yoke section for releasably drawing said first pair of clamp members together to clamp said first yoke section therebetween; a plurality of elongated support bars slidably received in each of said pair of clamp members and extending therebetween in engagement with the outer periphery of said first yoke section, said support bars being sized and positioned to support said laminations forming said leg and yoke sections.
 2. A transformer core assembly as set forth in claim 1, further comprising: a second pair of elongated clamp members extending parallel to opposite sides of a second yoke section; locking means extending between said second pair of elongated clamp members beyond each end of said second yoke section for releasably drawing said second pair of clamp members together to clamp said second yoke section therebetween.
 3. A transformer core assembly as set forth in claim 2, further comprising: force transfer means positioned adjacent at least two diagonally opposite corners of said transformer assembly and interconnecting predetermined ones of one of said pairs of clamp members with corresponding ones of the other of said pair of clamp members.
 4. A transformer core assembly as set forth in claim 3, wherein: each of said clamp members includes a first portion extending in juxtaposition to the corresponding yoke section and a second portion extending normally to the corresponding yoke section; said force transfer means includes a plurality of elongated bolts; each of said bolts being interconnected with a first portion of one of said first pair of clamp members and interconnected with a second portion of a corresponding one of said second pair of clamp members.
 5. A transformer core assembly as set forth in claim 4, wherein: each of said second pair of clamp members defines means for connection of a transformer core lift mechanism adjacent the interconnection that one of said second pair of clamp members and a corresponding bolt.
 6. A transformer core assembly as set forth in claim 1, wherein: each of said first pair of clamp members has a first portion extending in juxtaposition to said first yoke section and a second portion extending normally to said first yoke section; the first portion of each of said first pair of clamp members being apertured; each of said support bars extending through an aperature in a first portion and engaging a corresponding second section. 